Research Of Key Technologies In The Ethernet Control Systems

With the rapid development of the integrated circuit, the computer, the Internet and Ethernet, more and more attention has recently been focused on the application of the Ethernet in the domain of automatic control. The Ehernet control systems (ECS), a new class of the networked control systems (NCS), have been becoming the mainstream and the hottest topic of the industrial automatic control system.The ECS is a product with combination of computer, Ethernet network and automation technology, wherein the control loops is closed through the Ethernet network. The defining feature of an ECS is that information (reference input, plant output, control input, etc.) is exchanged using the Ethernet network among the control system components (sensors, controller:actuator, etc.). The prinlary advantages of ECS are reduced system wiring and the costs of Medias, ease of system diagnosis and maintenance, high of reliability and increased system agility. Regardless of ECS have been adopted in many industrial control areas for its attractive benefits, the performance of the ECS is always affected by the Ethernet network communication time-delay, which degrades the ECS control performance and destabilize the system and make the analysis and design of NCSs complex. Conventional control theories with many ideal assumptions, such as equal-distance sensing, synchronized control, and nondelayed sensing and actuation, must be reevaluated before they can be applied to ECS. Therefore, it is necessary that the advanced methodologies are developed to handle the communication time-delay in a closed-loop control system over the Ethernet network, what is more, many problems, such as the technique of the Ethernet interface for ECS node, the ECS system integratation etc, have to be solved in order to apply the ECS practically.In this dissertation, the exploratory research work has been done around the ECS, which include the analysis of the Ethernet communication time-delay performance, the modeling, stability analysis and the robust guaranted cost full state feedback controller design of the ECS, the technique of the Ethernet interface for ECS node and the ECS system integratation etc. The main contributions of this dissertation are summarized as follows:1. The time-delay comtrol system is the system that has time delay among the input signals, control signals and output singnals. The ECS is modeled as a time-delay control system. An asymptotic stability time-delay criterions of the ECS, the time-delay independent criterion and time-delay dependent criterion, are derived from the matrix norm inequality, the theory of time-delay control system and a new constructed Lyapunov function, and a laconic line search algorithm to determine the max bound of the asymptotic stability time-delay is also presented. The experimet and the comparison analysis with the corresponding criterions show that the proposed criterions have the less conservatism.2. Asynchronous dynamical systems are systems that incorporate both discrete and continu-ous dynamics, with the discrete dynamics governed by finite automata, and the continuous dynamics repre-sented by ordinary dierential equations at each discrete state. The ECS is modeled as an asynchronous dynamical system with rate constraints on events. By applying the Lyapunov stability theory and the asynchronous dynamical system heory, the sufficient time-delay criterion and data packet dropout criterion for the exponential stability of the ECS are proposed and proved. A laconic linear matrix inequality (LMI) algorithm is also provided to d validate the stability of the ECS. The simulation shows that our method is effective.3. By regarding the effect of random time-delay to the ECS as the unknown uncertain parameter disturbance, the ECS is modeled as a discrete uncertain time-delay control system. A sufficient condition, the existing of robust guaranteed cost control law for the ECS was proved by Lyapunov theory and the robust control theory. The design method of the robust guaranteed cost control full state feedback controller for the ECS is also presented in terms of LMI. The simulation results show that the method is effective.4. The technique of the Ethernet interface for ECS node is studied. The structure of the hardware and the software of the Micro-Embedded control System are presented. The solution in which the Micro-Embedded control System accesses to the Ethernet is proposed. The methods of simplifying the TCP/IP Protocol and constructing the WEB sever by software in the Micro-Embedded control System are also discussed in dietal. The experiment system of Micro-Embedded control System is built with the MSP430F139 processor and the RTL8019AS Ethernet controller chip.5. A distributed heat-supply supervising and control system based on the TCP/IP network is introduced. The integrated principles of the system are given and the hardware and software of the system are designed and implemented. The difficult problems in the system development process are also discussed in detail. The system consists of three components:local controller, supervising and control center and supervisory terminal. The communication of the system, combined TCP/IP network is convenient to integrate with the enterprise information system. The structure of two level databases is used to provide a date buffer for the data communication and avoid data drop. A WEB server is constructed by Java Script Page (JSP) technology in the system, through which Engineers can remotely supervise and control the heat-supply system via a WWW browser.The system has been used in the field of the city heater supply supervisory control, it also has a great application foreground in the supervisory control field of industry manufacture, water conservancy, electric power and environment.